What is FAR / FSI?
Also called: FSI, FAR, floor space index, floor area ratio
FSI (floor space index), called FAR (floor area ratio) in Delhi, Haryana and much of north India, is the total floor area allowed on a plot divided by the plot's area. An FSI of 2.5 on a 1,000 sq m plot permits 2,500 sq m of construction.
Every city's development control rules set a base FSI by zone and road width, and then allow more on payment. Mumbai under DCPR 2034 is the clearest example: base FSI, plus premium FSI bought from the municipal corporation, plus TDR bought from landowners elsewhere, plus fungible area that lets balconies and other spaces be absorbed on payment of a premium. Delhi works from the Master Plan and the Unified Building Bye-Laws; Noida and Greater Noida from their authorities' building regulations; Bengaluru from the zoning regulations of its master plan.
For a buyer, FSI explains two things. First, why land prices vary so much between neighbouring plots: a plot fronting a wider road can carry more floor area, so it's worth more. Second, why a quiet project can suddenly get denser. A builder with unused or newly purchasable FSI may want to add floors or a tower after you've booked.
The RERA Act limits that. Under Section 14, the builder needs the written consent of at least two-thirds of the allottees before changing the sanctioned plans or structure of the building, other than minor changes. Many agreements still carry a clause in which you 'consent' in advance to future FSI use. Read that clause and strike it or narrow it if you can.
Ask the builder what FSI the project is using now and what the maximum permissible is. The gap is the risk.
A 2,000 sq m plot in the western suburbs of Mumbai with an effective FSI of 2.5 after premium and TDR can carry 5,000 sq m of built floor area. If the road is later widened and the permissible FSI rises, the society may be approached for extra floors.
Signing an agreement that gives the builder blanket rights over 'present and future FSI'. That clause is how a promised garden becomes Tower D.
Questions people ask about FAR / FSI
Is FAR the same as FSI?
Yes. They measure the same ratio. FAR is sometimes written as a whole number, so FAR 250 in Delhi means an FSI of 2.5.
Does FSI include the basement and parking?
Usually not. Most regulations exclude basements used for parking, stilts, lift machine rooms and some service areas from FSI, but the exact list varies by city.